Measuring Pavement Deflection Variance at Highway Speeds

Abstract

A new method for testing pavement condition combines laser/inertial profilometry of unloaded pavement with vibration measurements in a full loaded heavy truck at highway speed. Three types of results are obtained. 1: Truck wheel, frame and cab vibration, as well as driver seat vibration to be compared with exposure guidelines in ISO 2631-1 and limits in directive 2002/44/EC. 2: Three-dimensional road surface geometry data for simulation of ride and calculation of roughness indices. 3: Locations of potential pavement "soft spots". The latter is possible since large pavement deflection variance under the heavy truck cause a quite different vehicle vibration pattern than the pattern excited from the measured unloaded road surface profile. A tentative accuracy experiment has been done at 4 sites. Recorded seat vibration levels were very high, thus exceeding the EU Action Value in all test runs. The soft spot indications show reasonable repeatability, as well as reproducibility between different driving speeds and between spring time and autumn. Trueness is the most
difficult accuracy feature to estimate, since no ideal reference method is at hand neither for variance of local deflection under truck wheel, nor for global deflection under the entire truck. By comparison with FWD, coring and ground penetrating radar results, trueness seems promising. During the tests, a virtual tyre footprint sensor was used for road profiling. Evaluation showed it to bring a large improvement to profiling accuracy. The new high speed measurement method brings excellent opportunities for further research on the entire chain pavement-truck-ride quality interaction.